package demo3;

public class MyLinkedList {


    public static ListNode head;
    public static ListNode last;

    //头插法
    public void addFirst(int data){
        ListNode node = new ListNode(data);
        if (head == null){
            head = node;
            last = node;
        }else {
            node.next = head;
            head.prev = node;
            head = node;
        }


    }
    //尾插法
    public ListNode addLast(int data){
        ListNode node = new ListNode(data);
        if (last == null){
            last = node;
        }else {
            last.next = node;
            node.prev = last;
            last = node;
        }
        return last;

    }

    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        if (index<0 || index>size()){
            System.out.println("下标错误");
            return;
        }

        if (index==0){
            addFirst(data);
            return;
        }
        if (index==size()){
            addLast(data);
            return;
        }

        ListNode cur = head;
        while (index>0){
            index--;
            cur=cur.next;
        }
        ListNode node = new ListNode(data);
        node.next = cur;
        node.prev = cur.prev;
        cur.prev.next = node;
        cur.prev = node;


    }


    //删除第一次出现关键字为key的节点
    public void remove(int key){
        ListNode cur = head;
        while (cur!=null){
            if (cur.val == key){
                //删除头结点
                if (cur == head){
                    head = head.next;
                    //只有一个节点的情况
                    if (head!=null){
                        head.prev = null;
                    }else {
                        last = null;
                    }

                }else{ //删除中间节点和尾巴节点
                    if (cur==last){
                        last = last.prev;
                        last.next = null;
                    }else {
                        cur.prev.next = cur.next;
                        cur.next.prev = cur.prev;
                    }

                }
                return;
            }else {
                cur = cur.next;
            }
        }
    }

    //删除所有值为key的节点
    public void removeAllKey(int key){
        ListNode cur = head;
        while (cur!=null){
            if (cur.val == key){
                //删除头结点
                if (cur == head){
                    head = head.next;
                    //只有一个节点的情况
                    if (head!=null){
                        head.prev = null;
                    }else {
                        last = null;
                    }

                }else{ //删除中间节点和尾巴节点
                    if (cur==last){
                        last = last.prev;
                        last.next = null;
                    }else {
                        cur.prev.next = cur.next;
                        cur.next.prev = cur.prev;
                    }

                }
            }
            cur = cur.next;
        }

    }








    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key,ListNode head){
        ListNode cur = head;
        while (cur !=null){
            if (cur.val == key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //得到单链表的长度
    public int size(){
        int count = 0;
        ListNode cur = head;
        while (cur!=null){
            count++;
            cur = cur.next;
        }
        return count;
    }
    public void display(ListNode head){
        ListNode cur = head;

        //正序
        while (cur!=null){
            System.out.print(cur.val+" ");
            cur = cur.next;
        }
        System.out.println();
//        //倒序
//        System.out.println();
//        while (lur!=null){
//            System.out.print(lur.val+" ");
//            lur = lur.prev;
//        }
//        System.out.println();


    }
    public void clear(){
        head = null;
        last = null;
    }



}
